Extrusion process



Feb. 3, 1942. G. F. TAYLOR EXTRUS ION PROCESS Filed Nov. 4, 1939 2Sheets-Sheet 1 Fig. 2.

inventor. George F Taylor,

b His Attorney.

- Feb. 3, 1942.. G. F. TAYLOR EXTRUSION PROCESS Filed Nov. 4, 1939 2SheecS-Sheet 2 Fig.

Ihvencor-: George F Taylor,

b fi y i y Hns Attorney.

Patented Feb. 3, 1942 EXTRUSION PROCESS George F. Taylor, Detroit,Mich., assignor to Carboloy Company, Inc., Detroit, Mich., a,corporation of New York Application November 4, 1939, Serial No. 302,901

20 Claims.

The present invention relates to extruded material and to a method forproducing the same. More particularly my invention relates to a methodfor extruding rods, tubes, shapes and the like which may consist of amixture of one or 'more hard metal carbides and a binder metal therefor.Sintered compositions consisting" of these ingredients are known ascemented carhides and generally are made by a cold press process whichcomprises pressing the dry mixed powdered ingredients in a steel moldand thereafter sintering the pressed material. If desired, however, themixed powdered ingredients may be manufactured into desired shapes by ahot press method which comprises applying pressure to the mixture whileit simultaneously is heated at its sintering temperature. The extrusiongun or apparatus which is employed in my process is disclosed andclaimed in my copending divisional application Serial No.. 341,757,filed June 21, 1940.

While the present process is applicable to metals and alloys generally,as well as to nonmetallic compositions such as porcelain etc., forsimplicity and brevity it will be described only as applied to cementedcarbide compositions and particularly as applied to a cemented carbidewhich consists of about 3 to 25% binder metal of the iron group with theremainder tungsten carbide.

It is one of the objects of the present invention to produce extrudedcemented carbides compositions which when sintered are hard, dense,strong and substantially free from cracks or porosity. It is a furtherobject of my invention to produce various shapes of extruded materialssuch as rods, tubes, spirals, twist drills and the A vertical crosssection of apparatus employed in carrying out my improved process; Fig.3 is a vertical cross section of a die employed in the production oftubes; Fig. 4 is a vertical elevation partly broken away illustratingthe delivery of extruded material onto a movable receiving table; whileFig. 5 is a vertical elevation partly broken away of an apparatuswhereby shapes such as spirals, drills or the like may be extruded.

In carrying out my improved process, powdered ingredients, which in themanufacture of hard metal compositions such as cemented carbide may befor example powdered tungsten carbide and cobalt, are placed in a ballmill together with a quantity of dry starch or equivalent material whichis capable of acting, when wet, as a plasticizing medium. The quantityof starch employed may vary but generally will not exceed about 1.75% byweight of the mixed tungsten carbide and cobalt. I may employ cassavastarch although other starches and other plasticizing agents such ascasein or equivalent material may be employed if desired as a bond forthe metallic particles. The powdered ingredients are placed in the ballmill with sufilcient alcohol to cover the powder and tumblers andproduce a thin sludge and thenball milled until a very intimate mixtureis obtained. Instead of alcohol, acetone, ether, or other material whichwets the starch but does not produce a change in its properties may beemployed. Thetumblers employed in the mill generally are very small inorder that the particle size of the hard metal particles may remainsubstantially unchanged during mixing with the starch. A mixing periodof about twelve hours gives satisfactory results but this time may beincreased or decreased as desired. After the mixture has been ballmilled to the desired ex tent it is placed in an oven and dried usuallyfor about three hours at a temperature of about C. The temperatureemployed should not be high enough to oxidize the metal particles orscorch the starch and preferably should not exceed about C, Aftersubstantially all the alcohol has been driven off, a small quantity of amixture of about 80% alcohol and 20% glycerine is added to the mixedpowdered ingredients. Only enough alcohol and glycerine mixture, forexample about 0.17% is added to make the mixed powdered ingredientssomewhat cohesive. Instead of alcohol any equivalent liquid which, ashereinbefore pointed out, does not dissolve or otherwise change theproperties of the starch or the other powdered ingredients may beemployed.

The mixture is now pressed into flat plate-like members which may have aslight convexity.

Disk-s about one-quarter inch thick and one inch in diameter having asmall central hole 2 onequarter inch in diameter give satisfactoryresults. The disks or plates preferably should be compressed hard enoughto permit handling without breaking but should not be compressed socompactly that when subsequently immersed in a water and glycerinesolution, as hereinafter ,set

forth, the solution will not penetrate thoroughly into the disks and insuflicient quantity to satisfy the starch and form a bond of the properconsistency.

The pressed disks I are threaded onto a steel rod 3 and inserted in acylindrical metal tube or container 4. The container 4 has a pluralityof circumferentially arranged substantially equally spacedlongitudinally extending openings, not shown, which extend from thelower end of the container 4 to a point adjacent the top thereof. Theseopenings permit the escape of water from the disks I when they aresubjected to pressure during the extrusion process. Container 4 isprovided with screw threads 5 at its lower end which engage a perforatedclosure member 6. The upper end of the container is screw threaded, asindicated at I. After the disks have been inserted in the container 4the rod 3 is removed and a fiat felt disk 8 placed on the top of thedisks. A screw-threaded cap 9 provided with openings I0 extendingtherethrough is applied to the upper end of the container 4. The disks Ihave a diame- The loaded container 4 is positioned within a cylindricalmetal member or container II which is supported on and soldered orwelded to a metal base plate I2 which in turn is supported on aninsulating plate I2. The container 4 is supported within the member IIupon spaced metal blocks I3 which are positioned on a metal ring I4secured in position at the lower end of the member II. Metal blocks I5space the container 4 at its upper end from the cylindrical member II.The upper end of the cylindrical member II is provided with a closuremember I'6 which seats against a lead gasket IT. A screw cap I8 engagescooperating screw threads on the member II while. a pair of screws I 9which extend through cap I8 are adapted to exert pressure on the closuremember I6 and force it against the lead gasket II.

The cylindrical containers 4 and II are arranged concentrically within athird cylindrical metal container which is also mounted on and rigidlysecured to the base I2. The container 20 is covered with thickinsulating material 2| and provided at its upper end with an insulatedcap or closure member 22. Three equally spaced pins 23 support the upperend of container II and position it centrally in the container 20. Pipes23' and 24 are connected respectively to the lower and upper ends of thecontainer 20 and to a pump, not shown, which is adapted to circulate oilthrough the container. Pipe 25 supplies a water-glycerine solution tocontainers 4 and II. A pipe 26 is connected to a source of distilledwater, while pipe 21 is connected to an evacuating pump.

When the loaded container 4 has been positioned within container I I,the closure member I6, which is rigidly secured to pipe 21, is appliedto the upper end of container I'I and forced into intimate contacttherewith by means ofthe screw cap I8 and screws I9. The insulating cap22 is then applied to the top of the container 20 and connections madeto a water supply and evacuating pump through pipes 26 and 21respectively. Hot oil having a temperature of about 120 to 180 C. isadmitted to container 20 and circulated therethrough for about one houror longer if desired. After the container has been filled with hot oil,evacuation of containers 4 and II is initiated through pipe 21. Theprocess of evacuation maybe discontinued for short periods from time totime and on each such occasion a very small quantity of distilled wateris admitted'to the containers 4 and II where it is immediately convertedinto steam having any desired pressure depending upon the amount ofwater forced in. A steam pressure of about 100 pounds is desirable inorder that the steam may penetrate all intergranular spaces of the disksI and purge them of air or other non-condensible gases. After eachadmission of water or steam the evacuation of containers 4 and H isresumed until the desired flnal degree of vacuum is obtained. The hotoil in container 2II is now drawn off through pipe 23 and, with thevacuum still on in containers 4 and II, refrigerated oil is admitted tocontainer 20 through pipe 23' and circulated through the container inthe same manner as the hot oil. When disks I have been cooled to atemperature of about -8 C. the vacuum in containers 4 and II is shut offand a mixture of water and glycerine containing about v 15 to 25%glycerine, and having a temperature of about -8 C. is admitted slowly tothe containers 4 and I I through a small pipe 25 until container II isentirely filled and disks I saturated, care being taken to prevent anysudden inrush of the water-glycerine solution. The glycerine lowers thefreezing point of the water and facilitates the penetration of the waterinto the disks I. It also permits subsequent uniform drying andhardening and prevents cracking of the extruded material during drying.I prefer to employ a mixture of glycerine and water. However, inextruding very small rods or tubing having a wall thickness of about 1:of an inch or less the use of glycerine may be omitted if desired. Thesteel pin 3 previously removed from the disks I is reinserted in thecentral hole 2 at this time, and the disks I reheated to a temperatureof about 80 to 95 C. for about ten minutes to cook the starch. Theheating may be accomplished in various ways. A convenient means fordoing so is to raise the temperature of the oil surrounding container IIto a temperature of about 95 C. or, if desired, cold oil may be drainedand replaced with hot oil having a temperature of about 80 to 95 C.allowing containers II and 4 to remain in the hot bath until the heathas penetratedto the disks I and cooked all of the starch therein.

After the starch has been cooked the loaded tube 4 is removed fromcontainer II and placed .in the extrusion gun designated as a whole bynumeral 28. The gun comprises a relatively heavy steel casing 29, aplunger 30, a connector 3!, and a die 32. The plunger 3% has a centralopening therethrough to accommodate the steel pin 3 and is provided atits lower end with a pair of spaced leather washers 33 and 34. A washer35 is positioned between the upper end of the casing 29 and a screw ring36 which has inner and outer screw threads thereon. Ring 36 engages thescrew threads 'I on container 4. A second screw ring 31 engages theouter threads on ring 36 and the screw threads on the upper end of thecasing 29; The lower end of the steel pin 3 is in the shape of a'chiselas indicated at 38 in Fig. 1 so that it cannot close the small openingor passage 39 extending'through the connector 3|. The connector 3| isscrew threaded at its opposite' jends' for connection respectively withcasing 29 of the extrusion gun and the die 32.

Die 32 comprises 'anozzle 40 outwardly flanged at its inner end to fitagainst an'jinturned flange 4| on the end of a'sleeve 42 .whichis joinedto the connector 3|- by means of screw threads. A ring 43 is positionedagainst the outwardly extending flange on the nozzle 40. The ring may beprovided, if desired, with a central circular portion 44 supported onfour thin radial arms.

A ring 45 abuts the outer end of the connector 3|. Between rings 43 and45 a series of wire screens 46 are positioned. These screens vary inmesh from about 35 to 65, the coarsest screen being positioned at theend nearest the connector 3| and the finest screen near the end of thenozzle 40. The meshes of the successive screens in the series vary andmay be substantially as follows 352048-20552065. The 20 mesh screensserve as separators between the other screens and are employed for thepurpose of preventing clogging in the screens.

When pressure is applied to plunger 30 the material in the container 4is forced through the smallpassage 39 in connector 3|. As the materialcomes out of the passage 39 it strikes the first of the screens 46 andspreads'over it in the space provided by ring 45. Further pressure onplunger 30 forces the material through the successive screens 46. Byvarying the mesh of the successive screens, as indicated above, thematerial forced through them becomes progressively more limp andplastic. The material forced through screens 46 enters nozzle 40 of thedie 32. The nozzle, illustrated in Fig. 1, is adapted for the productionof solid rods and is provided with a rounded portion 41 at its inner endto permit the free passage of material from the outer edge portions ofthe screens 46.

As the extruded material 48 comes out of the die 32, it is depositedonto a carriage consisting of parallel adjacent rollers, one of which isindicated at 49 in Fig. 4. The rollers are mounted on a platform 50which is movable in a longitudinal direction on wheels mounted onbearings 52. The platform 50 and rollers 49 are moved by any suitablemeans in a straight line a ar-p66 the same speed as the extrudedmaterial.

truded material. The extrusion die 53 disclosed in Fig. 5 comprises aholder 54 whichin turn is secured to the end of a metal tube 55. Tube 55opens into the extruding gun 28 which contains tube 4 which in turncontains the material to be extruded. A series of wire screens similarto the screens 46 are positioned within the die 53. The materialextruded through the die is in the formof a spiral and rotates the samenumber of times per unit length as the pitch thereof. To compensate forthis rotation the extruded material is deposited onto two adjacentparallel rollers 56 one of which is provided at one end thereof with alongitudinal slot in which a spiral strip of metal 51 is fitted so thatas rollers '56 are moved forward on their support they rotate at Therollers 56 are geared together so that both rotate in the samedirection. Another purpose of rollers 56 is to provide an easy means forturning over the larger sized extruded rods so that they may be paintedor brushed if desired with a water-glycerine solution to thereby obtainuniform drying. The material which is extruded through die 53 is driedand sintered as hereinbefore pointed out.

Various forms of dies may be made for ex- I truding different shapes. Inthe manufacture of and in the same direction and at the same speed asthe extruded material 48. After the material has been extruded onto therollers 49 to the desired extent it is thereafter dried. The rate ofdrying which can be maintained without danger of cracking depends uponthe size of the extruded article. Small objects or rods up to athickness of about one-eighth inch may be dried in the open air. Largerobjects generally are enclosed and heated in a closely fitting graphiteboat which surrounds the extruded material. An electric current may bepassed through the carbon boat to heat the extruded material at atemperature of about 70 to 95 C. A heating period of about 3 to 12 hoursgenerally is sufiicient to remove any water from the extruded material.Thereafter the extruded material is further heated in the carbon boat ata temperature of about 150 C. for about 24 hours or longer if desired.This latter heat treatment evaporates any glycerine in the extrudedmaterial. Thereafter the extruded material is placed in a graphite boat,covered with Alundum and sintered in a welLknown manner into a hard,dense= a die for extruding a spiral such as illustrated in Fig. 5, atwist drill bit is placed in a vertical position in a mold. Fused metal,for example type metal, is poured into the mold and flows around thedrill bit. After the type metal solidifies the bit is forced out of themold. The die thus formed is an exact negative of the object to beproduced.

In the manufacture of tubular products, a die 58 (Fig. 3) may beemployed. This die comprises a casing 59 and a mandrel 60. The latter isprovided at its upper end with a depressed portionGl. A central opening62 extends lengthwise through a mandrel and terminates at its lower endin four or more passageways 63 of smaller dimension than. the centralopening 62. The passageways 63 preferably open into a slightly enlargedspace 64 formed between the casing and mandrel. This latter space isgradually reduced in size as it approaches the end of the die.

The die 58 may be substituted in Fig. 1 forthe die 32 and provided witha series ofscreens 46 similar to those employed with the die 32. Whenpaste material is extruded through die 58 the diameter of the opening inthe end of the casing 59 determines the outside diameter of the tube tobe extruded while the diameter of the lower end portion of the mandrelwill determine the inside diameter of the extruded material. In

- order to center the mandrel 6,0 accurately within the casing 59 themandrel is provided at its upper and lower end portions with bearingrings 65 and 66.

For the production of certain articles of manufacture, the processhereinbefore disclosed may be simplified for example the tube 4 may befilled with disks or plates of pressed powdered materials and, withoutevacuating the gases from the tube and disks therein, the loaded tube iscooled down to a relatively low temperature, for example about *8 C. andthen placedin a jar or other suitable receptacle. A water-glycerinesolution such as hereinbefore mentioned, and which is likewise at a lowtemperature, for example about 8 C. is then slowly dripped into the jarso as to first wet the bottomv of the stack of disks in the container 4.The rate at which the water- ,is heated to cook the starch andthesubsequent steps of, the process are then carried out in the mannerhereinbefore set forth.

In extruding rods having a relatively large diameter, for examplegreater than diameter,

the usual short nozzle 40 may be replaced by a longer one which may besubstantially equal to the length of the rodto be extruded. The pastematerial in container 4 is then extruded into the nozzle. To remove thepaste material from the nozzle into which it has been extruded,container 7 l is filled with paraflin which is extruded into the nozzleto force out the paste material therein. If

desired, a cork or similar obstruction may be placed at the entrance ofthe long nozzle so as to offer resistance and cause the extruded pasteto be compacted very closely. A second cork may be placed in the nozzleto separate the paste therein from the parafiin which is employed toforce the paste out of they tube.

Ordinarily it may be found desirable to place an obstruction such as acork in the throat of any die employed in my improved extrusion process.When pressure is then applied to the plunger 30 the obstruction in thedie not only causes the strands of extruded material to be welded butcauses the paste stream to spread I out and fill all spaces in the dieand as a result the extruded material will contain little, if any, air.

Letters Patent of the United States, is:

1. In an extrusion process, the steps which comprise mixing ingredientsto be extruded with a, plasticising agent, pressing the mixture into adesired shape, removing gases from said material, and thereafterextruding it.

2. In an extrusion process, the steps which comprise mixing ingredientsto be extruded with starch and alcohol or its equivalent, drying themixture, pressing it into a compact body, removing gases therefrom, andthereafter extruding the pressed material.

3. In an extrusion process, the steps which comprise mixing ingredientsto be extruded with starch, pressing the mixture into a compact body,removing gases therefrom, impregnating the pressed material with aliquid to render it plastic and thereafter extruding the pressedmaterial.

4. In an extrusion process, the steps which comprise adding dry starchto pulverized metallic material, mixing said material and starch inalcohol or its equivalent, drying the mixture under non-oxidizingconditions, pressing the mixture into a compact body, removing gasesfrom said pressed material, impregnating the pressed material with amixture of water and glycerine, cooking the starch in said pressedmaterial, extruding the pressed material, slowly drying the extrudedmaterial, and thereafter sinteringit.

5. In an extrusion process in which water and glycerine have been addedto the material to be extruded, the steps which comprise drying theextruded material for several hours at a tempera- What I claim as newand desire to secure by ture in the neighborhood of 70 C. and thereafterheating the material for several hours at a temperature in theneighborhood of 150 C.

6. In an extrusion process, the steps which comprise adding dry starchto' the material to be extruded and thereafter mixing said material andstarch in alcohol.

4 7. In an extrusion process, the steps which comprise adding dry starchto the material to be.

extruded, wet mixing said material and starch in alcohol, drying themixture, pressing it into plate-like members, impregnating said memberswith water and thereafter extruding them.

8. In an extrusion process, the steps which comprise wet mixing thematerial to be extruded with starch and alcohol, drying the mixture,pressing it into plate-like'members, removing residual gases from saidmembers, impregnating said members with a water. and glycerine solution,and thereafter extruding the material in said members through a die.

9. In an extrusion process, the steps which comprise mixing the materialto be extruded with starch and alcohol, drying the mixture, pressing itinto plate-like members, supporting a stack of said members in a holder,removing residual gases from said members, cooling the members to arelatively low temperature, impregnating them with a mixture ofglycerine and water, cooking the starch in said members and extrudingthe material in said members.

10. In an extrusion process, the steps which comprise mixing thematerial to be extruded with dry starch and alcohol, drying the mixture,pressing the mixture into a stack consisting of a plurality ofplate-like members, removing residual gases from said members, coolingthe members to a temperature in the neighborhood of 0 C., impregnatingthem with a mixture of water and glycerine, cooking the starch in saidmembers and thereafter extruding the material in said members through adie and onto a support movable in the direction of the extrudedmaterial.

11. In an extrusion process, the steps which comprise mixing thematerial to be extruded in the starch and alcohol, drying the mixture,pressing it into plate-like members, stacking said members in-a tube,removing residual gases from said stacked members, cooling the membersto a relatively low temperature and impregnating them with a mixture ofglycerine and water, cooking the starch in said members at a temperaturebelow about C., andextruding the material in said members successivelythrough a series of wire mesh screens and a die.

12. In an extrusion process, the steps which comprise pressing a mixtureof the metal and starch into ring-shaped discs, stacking said discs in atube, removing residual gases from said stacked disc's, cooling thediscs to a relatively low temperature and then impregnating them with amixture of glycerine and water, cooking the starch in said discs at atemperature below about 95 C., and extruding thematerial in said discsonto a supporting member movable at substantially the same rate and L1the same direction as the extruded material.

13. In an extrusion process, the steps which comprise applying pressureto a pressed, powdered mixture to thereby force said material through adie and onto a transversely rotatable support longitudinally movable inthe same direction and at substantially the same speed as I the extrudedmaterial.

14. In an extrusion process, the steps which comprise applying pressureto a pressed, powder'ed mixture to thereoy force said materialsuccessively through a series of wire screens of varying mesh and anextrusion die.

15. In an extrusion process, the steps which comprise mixing the metalwith starch, pressing the mixture into plate-like members, removingresidual gases from said members, cooling them to a relatively lowtemperature, introducing a mixture of water and glycerine into themembers, cooking the starch in said members, and extruding the materialin them successively through a series of wire mesh screens and a die,and then onto a supporting member movable in, the same direction and atthe same rate as the extruded metal.

16. A process for extruding cemented carbide composition which comprisesmixing the ingredients of said composition with dry starch and alcohol,heating the mixture to remove the alcohol, thereafter adding suflicientinert liquid to the mixture to make it cohesive, pressing the mixtureinto plate-like members, placing said members in a container, removingresidual gases from said members, cooling them to a relatively lowtemperature and then impregnating them with a mixture of water andglycerine, cooking the starch in said members, and extruding thematerial in said members successively through a series of wire meshscreens and a die, and onto a support movable in the same direction andat substantially the same speed as the extruded metal.

17. In an extrusion process in which the material to be extruded hasbeen impregnated with a solution of water and glycerine, the steps whichcomprise enclosing the extruded material in a container and heating itat a temperature not being farthest away from said die.

19. In a process for extruding shapes such as spirals and the like, thesteps which comprise applying pressure to a powdered mixture to therebyforce said material through a die capable .of imparting the desiredshape to the extruded material and onto a support longitudinally movablein the same direction and at substantially the same speed as theextruded material, and compensating for the rotation of the extrudedmaterial as it is deposited onto said support.

20. In a process for manufacturing sintered bodies, the steps whichcomprise mixing ingredients to be sintered with starch and alcohol orits equivalent, drying the mixture, pressing it into a compact body,removing gases from the compact body, applying further pressure to saidbody to thereby form it into a desired shape, slowly drying said bodyand thereafter sinterlng it into a compact mass.

GEORGE F. TAYLOR.

